Heater for a motor air conditioning system comprising at least one heat pipe

ABSTRACT

A heater ( 30 ) is designed for a motor vehicle air conditioning system ( 10 ) and has at least one heat exchanger tube ( 58 ) which produces a heat conducting connection ( 54 ) between a heat generator ( 52 ) and at least one heat releaser via a medium which vaporizes and condenses in the heat exchanger tube. In order to be able to produce the heater ( 30 ) more economically, the heat generator ( 52 ) is made with an extruded profile ( 62, 84 ) to which at least one heat exchanger tube ( 58 ) is coupled by a heat conducting connection.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a heater for a motor vehicle airconditioning system with at least one heat exchanger tube which producesa heat conducting connection between a heat generating means with aheating element and at least one heat releasing means via a medium whichvaporizes and condenses in the heat exchanger tube. Furthermore, theinvention relates to an air conditioning system for a vehicle with sucha heater, a motor vehicle with such an air conditioning system, and aprocess for producing a heater for such a motor vehicle air conditioningsystem.

[0003] 2. Field of the Invention

[0004] Heaters of the initially mentioned type are used in motor vehicleair conditioning systems in order to be able to heat a liquid or gaseousheat transfer medium independently of the internal combustion engine ofthe motor vehicle. With the heated heat transfer medium, for example,ambient air, the passenger compartment of the motor vehicle can beheated up relatively quickly and especially the windows of the vehiclecan be defrosted. These are so-called defrosters.

[0005] In an electrical heater, as is known from published EuropeanPatent Application No. EP 0 243 077 A2, in its heat exchanger, there arePTC heating elements and radiator elements with ribs arranged in layers.The PTC heating elements heat the radiator elements in their immediatevicinity through which ambient air flows. On one edge of the heater,electrical contacts for the PTC heating elements are formed.

[0006] These heaters automatically limit their output, when a certainthreshold temperature is reached, by the rise of the resistance of thePTC heating elements. If a high enough voltage is applied to the PTCceramic so that the ceramic is heated up by the current flow, anequilibrium state occurs between the supplied electrical power and thedelivered thermal power. The ceramic cannot assume just any hightemperatures. The resistance increases in super proportion due to thespecial resistance temperature characteristic of the PTC ceramic and theelectrical current and output are limited.

[0007] The described property of the PTC ceramic can be ideally used forheating applications. PTC heating elements can be used asself-regulating dynamic heating elements. Therefore, with PTC heatingelements, the requirement of the vehicle manufacturer can be satisfiedthat the electrical heater with the outlet flaps closed and with fullheat output due to the danger of melting and fire may not exceed athreshold temperature from roughly 150° C. to 165° C.

[0008] However, known electrical heaters have disadvantages with respectto their construction. Thus, long electrical feed lines for highcurrents are necessary for the PTC heating elements which aredistributed in the heat exchanger of the heater. Furthermore, thedivision of the heat output in the form of the PTC heating elementsresults in the problem that the heat output cannot be optionallydistributed uniformly over the heat exchanger of the heater. Rather,unoccupied PTC locations, as necessarily form due to the high resistancetolerance of +/−35% of the PTC heating elements, lead to cold spots onthe surface of the heater. These cold spots can be pulled as cold airplumes through the air channels of the air conditioning system.

[0009] Integration of the PTC heating elements into the heat exchangeralso leads to the heat exchanger being not homogeneous, but beingcomposed of several materials. These materials, for example, aluminum,plastic and ceramic, can only be separated from the heat exchanger andrecycled with difficulty after the service life of the heater hasexpired.

[0010] Furthermore, the use of PTC heating elements leads to highspecific heating costs. PTC ceramic is an expensive material with highspecific weight. For reliable contact-making, complex mechanicalstructures in the form of steel frames or the like are necessary on theedge of the heater.

[0011] Electrical headers are also known in which heating elements areelectronically controlled. For control purposes, control transistorswith a strength of the control currents of roughly 70 to 140 amperes areused. These control transistors produce exhaust heat of roughly 70 wattswhich is advantageously also fed into the heat exchanger of the heater.However, the delivery of heat requires high structural effort.Therefore, in general, control transistors are used which have a powerloss as low as possible. The control currents of high intensity must beswitched with repetition rates of, for example, 30 Hz and 100 Hz. Thisleads to considerable problems with respect to the electromagneticcompatibility of the heater within the vehicle.

[0012] A generic heater is known from the Patent Abstracts of Japan6365752 A. There, a fluid heater is described in which heat can betransported to ribs in a heat accumulator and to ribs in a flow heatexchanger with the heat pipe of the PTC heating element. The PTC heatingelement is used as a heat generating means from which the heat istransported to the ribs as the heat releasing means via the heat pipe.The object is to store heat in a heat accumulator over a long intervalby special techniques. In the latter heater there is the problem that itis relatively expensive to produce. In particular, the configuration ofthe heat generating means is complex.

[0013] Published German Patent Application DE 197 43 427 A1 discloses aheat exchanger which is made in the classical execution without a heatexchanger tube, with a plurality of flat tubes which are arrangedparallel to one another for guiding a cooling medium. The ends of theflat tubes are bent, are placed tightly against one another and are eachconnected to a connecting pipe piece which is used as the collectingpipe for the cooling medium. The collecting pipe is made in an extrusionprocess as a profile pipe section. The object is to form a fluid-tightconnection between the flat tubes and the collecting pipe here. Heat isconversely not routed via the connection between the flat tube and thecollecting pipe.

[0014] German Patent DE 31 43 334 C2 discloses a heat exchanger with abundle of parallel running pipes which are exposed transversely to air,the pipes being positioned in the manner of heat exchanger tubes betweentwo heat exchanger heads. Within the individual heat exchanger head,between two adjacent pipes, there is a heat exchanger plate which ismade as an extruded profile in the form of a double web plate withseveral channels which run parallel next to one another. The heatexchanger plates extend transversely to the lengthwise direction of therespective heat exchanger head. On the lengthwise sides of each heatexchanger head, there are lengthwise channels which are connected to thechannels of the transversely extending heat exchanger plates to carryliquid.

[0015] Published German Patent Application DE 40 14 510 A1 discloses amotor vehicle heating system and a process for its operation in which aheat exchanger tube is used as a connection between a burner as the heatgenerating means and a heat exchanger as the heat releasing means.

[0016] Published German Patent Application DE 199 11 547 A1 discloses anelectrical heating means for a motor vehicle which is composed ofseveral heating elements which are arranged parallel and which have PTCheating elements, and of corrugated ribs which adjoin the heatingelements in a heat conducting connection.

SUMMARY OF THE INVENTION

[0017] An object of the present invention is to devise a heater of theinitially mentioned type that it can be economically produced. In thisway, the total production costs of the pertinent air conditioning systemof a motor vehicle will be reduced.

[0018] This object is achieved in accordance with the invention with theinitially mentioned heater in which the heat generating means is madewith an extruded profile to which at least one heat exchanger tube iscoupled by heat conduction. Furthermore, the object is achieved with anair conditioning system for a motor vehicle in which such a heater ofthe invention is incorporated and with a motor vehicle which has such anair conditioning system according to the invention. In addition, aprocess with the steps of producing a heat conducting connection betweenat least one heat exchanger tube and an extruded profile, with anopening in its lengthwise direction, and insertion of at least one heatconductor or a PTC heating element into the opening, creates oneapproach to the object.

[0019] The heat generating means of the heater in accordance with theinvention is provided with a housing which is produced as an elongatedextruded profile. The extruded profile can be economically produced,meet high dimensional requirements and enable great freedom in theconfiguration of the profile cross sections. In addition, for extrusionpurposes, in particular, aluminum alloys can be used which have highthermal conductivity. The extruded profile of the invention leads to anespecially uniform heat distribution on the heat generating means.Therefore, in a heater with several heat exchanger tubes, they areuniformly heated and formation of cold plumes on the heat releasingmeans of the heater is thus avoided.

[0020] For the profile of the invention, it is especially feasible if itis produced by extrusion in two areas.

[0021] The first area is where the heating element, for example, a heatconductor, can be located within the heat generating means. This firstarea extends over almost the entire length of the extruded profile. Inthe extruded profile, elongated cavities can be formed especiallyadvantageously. Such a cavity can be used in the extruded profile to theinvention in order to insert and fix the heat conductor in it, forexample. Fixing can take place with a heat conducting mass which isadded to the cavity between the extruded profile and the heat conductor.In addition, the extruded profile can be pressed. All these arrangementscreate a combination of the housing and heating elements which can beproduced easily and economically as a heat generating means.

[0022] The second area is the interface between the heat generatingmeans and the heat exchanger tube. This interface must conduct heatespecially well. This second area can be made on an extruded profile bytransverse openings which can be formed easily, and moreover, preciselyin the profile. These openings can be punched or drilled, for example,in the extruded profile. The material of the extruded profile can besoldered or pressed with the heat exchanger tubes located in thetransverse openings in an economical, and moreover, controlled manner.Alternatively, the heat exchanger tubes can also be inserted in alengthwise groove of the extruded profile. A combination of thetransverse opening and lengthwise groove is also conceivable. In anycase, an extruded profile with this shape can be produced easily,economically, and moreover, with high dimensional accuracy.

[0023] In addition, on the extruded profile, there can very easily alsobe so-called function surfaces for mounting of electronic components.These function surfaces can be formed on the extruded profilesespecially well for mounting of transistors.

[0024] Furthermore, extruded profiles can be formed with the same toolalmost without added costs in different lengths. There can besystematically or modularly different lengths by which different heatertypes can be produced using only one tool.

[0025] For known heat exchangers with a liquid heat transfer mediumwhich have no heat exchanger tubes, to some extent extruded profileshave been used, because with them a fluid-tight connection was formed.According to the invention, between the heating element and the heatexchanger tube, there is no fluid-conducting connection so that heatmust be transported conductively according to the invention.

[0026] A principle aspect of the invention is, therefore, that severalproblems can be solved at the same time with an extruded profile. One ofthe problems is the question of how the heating element can be coupled,a second problem is the mounting of the heat exchanger tubes. Inaddition, the extruded profile forms the foundation for advantageousdevelopments and different heater types which can be produced especiallyeconomically.

[0027] The approach of the invention can be effectively used in heaterswith a high power density at the interface between the heat generatingmeans and the heat exchanger tube. As a result of the good thermalconductivity of the extruded profile used, a comparatively smalltemperature gradient in heat conduction can be achieved in this area.Therefore, the heat generating means according to the invention reacts,for example, especially quickly when the heat releasing means is dammed,by its slowing down.

[0028] In one advantageous development of the invention, in the extrudedprofile, at least one first opening is formed in its transversedirection for holding one end of the heat exchanger tube. As mentionedabove, these openings can be produced economically. The end of the heatexchanger tube is encompassed, in this configuration, by the extrudedprofile and a comparatively large heat transfer surface is formed.Alternatively, the heat exchanger tube with its end or its base can besoldered onto the heat generating means.

[0029] The aforementioned heat conducting connection between theextruded profile and the heat exchanger tube can be formed especiallyadvantageously by soldering. When soldering, a plurality of heatexchanger tubes can be coupled to the extruded profile in one process.In addition, cavities and gaps between the heat exchanger tube and theextruded profile are filled in soldering and thus good thermalconductivity of the connection is formed.

[0030] Alternatively or additionally, the heat conductive connectionbetween the extruded profile and the heat exchanger tube can be formedby caulking. Caulking offers especially the advantage that hightemperatures do not form and accordingly the heat generating meanscannot be damaged by high heating. Furthermore, a caulking process isgenerally very economical, and especially for production of largenumbers, it is the process of choice.

[0031] In the lengthwise direction of extruded profile, a second openingis advantageously formed for accommodating at least one PTC heatingelement or one heat conductor. The second opening can, as mentionedabove, be made with great freedom of configuration and therefore can beexactly matched to the shape required for one or more PTC heatingelements or a heat conductor.

[0032] A PTC heating element can be pushed into the opening and fixed init by pressing the extruded profile towards the PTC heating element andoptionally electrical contact can be made with it.

[0033] Furthermore, on the extruded profile of the invention, there isadvantageously at least one function surface for the mechanical,electrical or heat conducting connection of at least one PTC heatingelement or at least one heat conductor. Such a function surface inaccordance with the invention is a free by-product of the extrusionprocess. A means which is to be located in the heat generating means canbe thermally linked using the function surface, electrical contact canbe made with it, and moreover, it can be mechanically fixed. A functionsurface can be provided with an especially smooth surface using anextrusion process, which is advantageous especially for thermal andelectrical contact-making. On such a function surface, besides a PTCheating element or a heat conductor, an electrical controller, forexample, in the form of a control transistor, can be mounted.

[0034] The indicated second opening can moreover be made as a slot intowhich especially at least one PTC heating element is pushed in thetransverse direction of the extruded profile. Alternatively, heatingelements can also be pushed axially into the extruded profile.Generally, in the heater of a motor vehicle air conditioning systemthere can be a majority up to a plurality of PTC heating elements. Thistakes place in the described development by simply inserting theindividual PTC heating element radially into an axially pointed slot.The resulting short insertion path and high dimensional accuracy on theslot enable economical and moreover controlled production of the heaterwhich has been developed in this way.

[0035] At least one PTC heating element is furthermore advantageouslyheld in the slot by elastic pre-tensioning of the extruded profile. ThePTC heating element is pinched in the slot and is mechanically fixed byclamping. Moreover, between the clamped faces of the PTC heatingelements and the material of the extruded profile, outstanding heattransfer is formed. The clamping can be produced by elastic expansion ofthe extruded profile itself. Alternatively or additionally, there canspecially be a spring element in order to ensure clamping over theservice life of the heater.

[0036] Embodiments of the motor vehicle air conditioning system areexplained in detail below using the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 shows a cross section of an air conditioning system inaccordance with the invention,

[0038]FIG. 2 is a perspective view of the heater of the air conditioningsystem as shown in FIG. 1,

[0039]FIG. 3 shows a side view of a segment of a partially cutaway heatpipe of the heater as shown in FIG. 2,

[0040]FIG. 4 is an exploded perspective view of a first embodiment of anextruded profile with a heat generating means in accordance with theinvention of the heater shown in FIG. 2,

[0041]FIG. 5 shows a perspective view of a second embodiment of anextruded profile with a heat generating means of the invention for theheater as shown in FIG. 2,

[0042]FIG. 6 shows a cross section of a third embodiment of an extrudedprofile with a heat generating means according to the invention for theheater as shown in FIG. 2,

[0043]FIG. 7 shows a cross section of a fourth embodiment of an extrudedprofile with a heat generating means in accordance with the invention ofthe heater as shown in FIG. 2, and

[0044]FIG. 8 is a graph which illustrates the relationship between theresistance and temperature of a PTC ceramic.

DETAILED DESCRIPTION OF THE INVENTION

[0045]FIG. 1 shows an air conditioning system 10 for a motor vehicle 12in the form of a passenger car. The air conditioning system 10 isinstalled in the area of the dashboard 14 of the motor vehicle 12. ithas an air inlet 16 which is located between the hood 18 and thewindshield 20 of the vehicle 12. Underneath the air inlet 16 is a fan 22which delivers air from the vicinity of the motor vehicle 12 into theair conditioning box 24. The air conditioning box 24 is a space which islocated underneath the windshield 20 and in which there are two heatexchangers 26, 28 and a heater 30 in succession.

[0046] Air which has been conveyed by the fan 22 through the heatexchanger 26, 28 and the heater 30 and which has been optionally heated,then travels into diverse air channels 32, 34, 36 which are made in thedashboard 14. The air travels through the air channels 32, 34, 36 to theoutlet flaps 38, 40 and 42 and finally through air outlets 44, 46, and48 into the passenger compartment 50.

[0047] The heat exchangers 26, 28 are designed for liquid heat transfermedia, for example, the coolant of an internal combustion engine of themotor vehicle 12 (not shown). The liquid heat transfer media aredelivered by the heating or cooling system of the motor vehicle 12 (notshown) through the heat exchangers 26, 28.

[0048] The heater 30 is made as an electrical heater which heats airfrom the vicinity of the vehicle 12 if enough heat energy cannot be madeavailable by the remaining heating system of the vehicle 12. This is thecase, for example, when the coolant of the internal combustion engine iscold immediately after the engine starts. Furthermore, an electricalheater can be efficient or necessary when the motor vehicle 12 isprovided with a consumption-optimized internal combustion engine whichdelivers relatively little exhaust heat.

[0049]FIG. 2 illustrates the basic structure of the electrical heater 30of the invention.

[0050] The heater 30 has a single, essentially closed heat generatingmeans 52 which is connected to the heat conducting means 54 in the formof heat exchanger tubes. The heat exchanger tubes 58 are connected bythermal conduction to the heat releasing means 56 which are in the formof a plurality of ribs and form with them the heat exchanger of theheater 30.

[0051] The individual means 52, 54, 56 within the heater 30 formindividual modules which can be combined and matched individually to theribs depending on the required heat output and desired flow and spaceconditions. For the heat exchanger tubes 58 in combination with theribs, a conventional heat exchanger can be used, as is used, forexample, in water-air heat exchangers. The ribs can also extend betweentwo heat exchanger tubes 58 as corrugated or zig-zag sheets. One suchheat exchanger which is economical to produce is known, for example,from publishe European Patent Application EP 0 775 884 A3. The heatexchanger tubes 58 are round tubes. A configuration as flat tubes isalso advantageous. The aforementioned zig-zag ribs can also be coupledespecially well to these flat tubes.

[0052] The heat generating means 52 is located, in accordance with theinvention, on an edge of the heater 30. From the heat generating means52, several heat exchanger tubes 58 project perpendicularly to andthrough the plurality of ribs 56 which generally extend spaced parallelto the heat generating means 52. The heat pipes 58 therefore passthrough the ribs 56 essentially normal thereto.

[0053] Connections which are especially heat conductive are formedbetween the heat generating means 52 and the heat exchanger tubes 58 andbetween the heat exchanger tubes 58 and the heat releasing ribs 56.

[0054] The heat tubes 58 provided according to the invention, make itpossible for the heating elements of the heater 30 to be concentrated onone edge or at least in one area of its heat exchanger. The generatedheat can be distributed uniformly by the invention over the entiresurface of the heat exchanger by means of the heat exchanger tubes 58without formation of cold air plumes.

[0055]FIG. 3 illustrates the operation of a heat exchanger tube 58 as aheat conducting means 54 within the heater 30. Such a heat exchangertube is also called a heat pipe.

[0056] In the heat exchanger tube 58, which is shown broken-away in FIG.3, the heat is transported from bottom to top. In the bottom area of theheat exchanger tube 58, the heat generating means 52 is located as theheat source. The liquid which is located in the heat exchanger tube 58is vaporized by it. The liquid can be, for example, high-purity water.The vaporized liquid rises at high speed as steam in the heat exchangertube 58. This is illustrated with the arrow A.

[0057] The steam travels to points of a hollow cylindrical wall 60 ofthe heat exchanger tube 58 at which comparatively low temperaturesprevail because the heat exchanger tube 58 has been cooled there, forexample, by heat conduction to a rib (arrow B). At the colder locations,the steam condenses. The liquified steam flows as a liquid to the bottomarea of the heat exchanger tube 58 and back to the heat source locatedthere (arrow C). With re-vaporization of the liquid the described cycleof heat transport begins again.

[0058] The steam condenses on the heat exchanger tube 58 exactly wherethe colder locations of the wall 60 are located, therefore at thelocations where there is a heat demand. The wall 60 of the heatexchanger tube 58 is therefore almost homogeneously heated. A noticeabletemperature drop as is known in heat conduction in a solid generallycannot be noted. Large amounts of heat can be transported by the phasetransition between liquid and gas. The heat transport capacity of such aheat exchanger tube 58, as compared to solids with similar dimensions,is roughly 10 to 100 times higher.

[0059] The condensed liquid can be returned to the heat source also bycapillary action in, for example, a fine network on the inside of theheat exchanger tube 58. The heat exchanger tube 58 can also be operatedhorizontally.

[0060]FIG. 4 shows a first embodiment of a heat generating means 52 asis used for the heater 30 of the invention.

[0061] The heat generating means 52 has an extruded profile 62 ofaluminum alloy with an essentially cylindrical base body in which acylindrical lengthwise opening 64 is provided in the lengthwisedirection of the extruded profile 62 and three cylindrical transverseopenings 66 are formed transversely to the extruded profile.

[0062] The bottom ends of the heat exchanger tubes 58 are inserted andmounted in the transverse openings 66, being caulked or soldered thereto conduct heat.

[0063] The lengthwise opening 64 is used for accommodating an electricalheating element in the form of a heating rod 68. The heating rod 68 isprovided with a cylindrical pipe jacket 70 with a diameter which ismatched to the diameter of the lengthwise opening 64. In the pipe jacket70, there is an insulating mass 72. On the ends, the pipe jacket 70 issealed by ceramic end sleeves 74 on which a respective electricalterminal 76 is located with a terminal bolt 78. Between the terminalbolts 78, a heat conductor 80 is routed through the ceramic end sleeves74 and the insulating mass 72. In an embodiment which is not shown, thepipe jacket 70 is omitted and the heat conductor 80 and the insulatingmass 72 are inserted directly into the lengthwise opening 64 and fixedin it.

[0064] Using the heat conductor 80, in the operation of the heater 30with the heating rod 68, the extruded profile 62 can be heated. Theextruded profile 62 transfers the heat directly to the embedded ends ofthe heat exchanger tubes 58. The latter route the heat uniformly andquickly to the ribs which are used as heat releasing means 56.

[0065] On the extruded profile 62, finally, a flattened area 82 isformed as a so-called “function surface” by which the extruded profile62, and optionally the heat exchanger tubes 58 which are attached to itwith their ribs, can be mounted directly on a component of the vehicle12 or in an outside housing of the heater 30, which housing is notshown. The flattened area can also be used for mounting a controltransistor with which the heat output of the heat conductor 80 iselectrically controlled.

[0066]FIG. 5 shows a second embodiment of the heat generating means 52with an extruded profile 84 which is used to accommodate the PTC heatingelements 86.

[0067] The extruded profile 84 is made as a cylindrical base body inwhich a lengthwise slot 88 is formed and three cross openings 90 areformed transversely to the lengthwise slot 88. The cross openings 90 areused, in turn, to accommodate the ends of the heat exchanger tubes 58.

[0068] When the heater 30 is installed, the PTC heating elements 86 arepinched in the lengthwise slot 88. The extruded profile 84 in the areaof the lengthwise slot 88 is elastically widened for clamping, the PTCheating elements 86 are pushed in and the lengthwise slot 88 is allowedto elastically taper again.

[0069] Thus, between the extruded profile 84 and the PTC heatingelements 86, a highly heat conductive connection which is, moreover,suited for electrical contact-making is formed. Function surfaces whichare (not shown) are provided in the lengthwise slot 88 for this purpose.The PTC heating elements 86 make contact using a contact foil 92 whichadjoins one side of the PTC heating element 86 in the lengthwise slot 88and is electrically insulated against the extruded profile 84 using aninsulating foil 94.

[0070]FIG. 6 shows another embodiment of a heat generating means 52. Inthis embodiment, in the extruded profile 84, as explained above, atleast one cross opening 90 for accommodating one end of the heatexchanger tube 58 is formed.

[0071] Furthermore, in the extruded profile 84, a slot-shaped opening 96is formed as a lengthwise opening and is located in the lengthwisedirection of the heat exchanger tube 58 underneath its end. The PTCheating elements 86 are inserted in the opening 96 using a contact foil92 and an insulating foil 94, as explained above.

[0072] On the sides of the extruded profile 84, two flattened areas 98,100 are formed, on which the extruded profile 84 has been caulked orpressed in the direction toward the PTC heating elements 86. By thispressing, the PTC heating elements 86 are fixed mechanically to conductheat in the opening 96 and electrical contact-making on the contact foil92 is produced.

[0073]FIG. 7 shows an embodiment of a heat generating means 52 in whichin the extruded profile 84, underneath and next to the heat exchangertubes 58, has two openings 96 for accommodating the PTC heating elements86. In this arrangement, especially good heat release from the PTCheating elements 86 to the ends of the heat exchanger tubes 58 isprovided. The PTC heating elements 86 are inserted aligned in theopenings 96 such that their surfaces which are in direct contact withthe extruded profile 84 face toward the lengthwise axis of the heat pipe58. In an embodiment which is not shown, the indicated surfaces are eachaligned relative to the an end of the heat exchanger tube 58. Therefore,openings 96 are arranged in a V shape. In addition, the end of the heatexchanger tube 58 can be pressed flat and sealed. The transverse opening90 can be matched on its base to the shape of the flat-pressed heatexchanger tube 58. It is likewise V shaped in this area in crosssection.

[0074] On the sides of the extruded profile 84, analogously to theembodiment shown in FIG. 6, flat areas 98, 100 are formed. The extrudedprofile 84 is made stable in the area between the openings 96 such that,essentially it is not deformed during the pressing of the PTC heatingelements 86 in this area.

[0075] Alternatively, the extruded profile 84 can be made deformable ina controlled manner in the area between the two openings 96. Thedeformation process can be used to compress and seal at least one end ofthe heat pipe 58 which has been inserted into the cross opening 90before pressing.

[0076] The PTC heating elements 86 in the electrical heater 30 arecomponents which cause high costs as a result of their complexproduction and their more expensive material. Therefore, efforts aremade to operate the PTC heating element 86 with maximum output P. At aconstant supply voltage, due to P=U²/R, it means that the minimumresistance should be triggered on the resistance characteristic of thePTC heating elements 86.

[0077] The initially described equilibrium state between the resistanceand temperature on the PTC heating elements 86 and also the temperatureof the ceramic which has been reached there depend largely on the heatrelease to the vicinity. High heat outputs can be achieved only with afavorable heat conducting means 54 and thus an optimized and long-livedheater with PTC ceramic can be formed.

[0078] The combination of PTC heating elements 86 with heat exchangertubes 58 according to the invention leads to stronger release of heatfrom the PTC heating elements 86 than in the technologies used in thepast. As a result of the better heat conduction the temperaturedifference between the PTC heating elements 86 and the heat releasingmeans 56 of the heater 30 decreases. The PTC heating elements 86 cooloff. The associated increase of resistance allows the electrical outputto drop until a new equilibrium state is reached (see point 1 to point 2in FIG. 8). The PTC heating elements 86 would therefore work basicallyat a lower temperature.

[0079] However, a PTC ceramic with an especially low electricalresistance can be used. In this way, the output of the PTC heatingelements 86 is increased and thus the temperature rises again to theoptimum operating point 86 (see point 2 to point 3 in FIG. 8). At theoptimum operating point the PTC heating elements 86 are located in thevicinity of the point of lowest resistance of the PTC ceramic.

[0080] This means that the PTC heating elements 86 have the lowestinherent weight per delivered output. The use of heat exchanger tubes 58as claimed in the invention therefore offers the possibility ofsignificantly reducing the number and weight of the PTC heating elements86 together with contact-making at a constant heat output. The heatoutput can be greatly increased relative to the costs of the PTC heatingelements 86. Moreover, the heat generating means 52 can be madeespecially compact.

What is claimed is:
 1. Heater (30) for a motor vehicle air conditioningsystem (10) with at least one heat exchanger tube (58) which produces aheat conducting connection (54) between a heat generating means (52)with a heating element (80, 86) and at least one heat releasing means(56) via a medium which vaporizes and condenses in the heat exchangertube (58), characterized in that the heat generating means (52) is madewith an extruded profile (62, 84) to which at least one heat exchangertube (58) is coupled by heat conduction.
 2. Heater as claimed in claim1, wherein in the extruded profile (62, 84) in its transverse directionat least one first opening (66, 90) is formed for holding one end of theheat exchanger tube (58).
 3. Heater as claimed in claim 1 or 2, whereina heat conducting connection is formed between the extruded profile (62,84) and at least one heat exchanger tube (58) by soldering.
 4. Heater asclaimed in one of claims 1 to 3, wherein a heat conducting connection isformed between the extruded profile (62, 84) and at least one heatexchanger tube (58) by caulking.
 5. Heater as claimed in one of claims 1to 4, wherein in the extruded profile (62, 84) in its lengthwisedirection a second opening (64, 88, 96) is formed for accommodating atleast one heat conductor (80) or at least one PTC heating element (86).6. Heater as claimed in claim 5, wherein on the extruded profile (62,84) especially in the area of the second opening (64, 88, 96) there isat least one function surface for the mechanical, electrical or heatconducting connection of at least one heat conductor (80) or at leastone PTC heating element (86).
 7. Heater as claimed in claim 6 or 8,wherein the second opening is made as a slot (88) into which especiallyat least one PTC heating element (86) is pushed in the transversedirection of the extruded profile (84).
 8. Heater as claimed in claim 7,wherein at least one PTC heating element (86) is held in the slot (88)by elastic pretensioning of the extruded profile (84).
 9. Airconditioning system (10) for a motor vehicle (12) with a heater (30) asclaimed in one of claims 1 to
 8. 10. Motor vehicle (12) with an airconditioning system (10) as claimed in claim
 9. 11. Process forproducing a heater (30) for a motor vehicle air conditioning system (10)with the steps: producing a heat conducting connection between at leastone heat exchanger tube (58) and an extruded profile (62, 84), with anopening (64, 88, 96) made in its lengthwise direction, and insertion ofat least one heat conductor (80) or a PTC heating element (86) into theopening (64, 88, 96).